Plural cycle cam yarn winding process and packages produced thereby

ABSTRACT

A PROCESS FOR WINDING YARN INTO A CYLINDRICAL-BODIED PACKAGE WHEREIN THE YARN IS TRAVERSE WOUND IN LAYERS OF HELICAL COILS ON A BOBBIN WHEREIN THE COILS ARE LAID DOWN IN THEIR REVERSALS IN DIFFERENT SHAPED CURVES IN A REPEATING PROGRESSION THROUGHOUT THE WINDING OF THE PACKAGE. THE CORRESPONDING STROKE LENGTHS OF THE COILS WITH DIFFERENT SHAPED REVERSALS MAY ALSO BE OF DIFFERENT LENGTHS.

Sept. 20, 1971 R. l.. AKERS 3,606,197

PLURAL CYCLE CAM YARN WINDING PROCESS AND PACKAGES PRODUCED THEREBY Filed June 3, 1969 2 Sheets-Sheet 1 FIG. FIG. l uggs-* le ,5 WW lo Pm RH -RH I /Z 2 l 9,- 3 5 7 I* TYD ONEREV. a'

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\/A INVENTOR FOUR CYCLES RICHARD L. AKERS BY Wd www@ ATTORNEY sept 20, 1971 R. l.. AKI-:Rs 3,606,197

PLURAL CYCLE CAM YARN WINDING PR SS AND PACKAGES PRODUCED THEREB Filed June s, 1969 2 sheets-sheet 2 25 la F|.G.8 F|6.|o

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ATTORNEY United States Patent 3,606,197 PLURAL CYCLE CAM YARN WINDING PROCESS AND PACKAGES PRODUCED THEREBY Richard L. Akers, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. Filed .lune 3, 1969, Ser. No. 830,054 Int. Cl. B65h 54/28, 54/38 U.S. Cl. 242-176 7 Claims ABSTRACT F THE DISCLOSURE A process for winding yarn into a cylindrical-bodied package wherein the yarn is traverse Wound in layers of helical coils on a bobbin wherein the coils are laid down in their reversals in different shaped curves in a repeating progression throughout the winding of the package. The corresponding stroke lengths of the coils with different shaped reversals may also be of different lengths.

BACKGROUND OF THE INVENTION This invention relates to the cross-winding of yarns and more particularly to the winding of cylindrical yarn packages with improved formation and stability. Such packages are commonly formed by windups employing a surface drive. The drive roll is operated at a constant speed thus maintaining a constant surface velocity of the driven package despite the growth of the package as the filamentous material is wound thereon. A cam-actuated reciprocating traverse guide may be used to lay the yarn onto the bobbin in layers of helical coils either directly or by means of a print roll.

Package defects associated with currently used winding techniques appear to be related in some Way to yarn laydown at the reversals of the helical coils formed by successive traverse strokes in crosswinding a cylindrical yarn package.

In the past, attempts have been made to improve yarn distribution at and near the package ends, such as by superimposing an axial reciprocation on the primary traverse stroke or by changing the length of the transverse stroke cyclically by mechanical means. These approaches provide very limited dispersion patterns.

SUMMARY OF THE INVENTION It is an object of this invention to provide a cross-wound yarn package with improved formation and stability by forming separate reversals with differently shaped yarn configurations. The differently shaped reversals lare arranged in an alternate repeating progression throughout the package; for example, two or three of one kind of reversal followed by one or more of another kind repeated sequentially. Any sequential pair of reversals may also terminate at different stroke lengths.

According to the present invention, the above object is accomplished by providing a method of winding yarn on a bobbin that includes the steps of rotating the bobbin while simultaneously traversing the yarn axially of the bobbin through successive strokes to form la package of layers of helical coils. Each coil has substantially the same helix angle and is laid down at its reversal in a curve. The improvement comprises lying down the coils in their relversals in differently shaped curves in a repeating progression throughout the winding of the package. This is accomplished by having a plurality of different traverse cycles formed in the traverse cam according to the repeating progression desired. Preferably any yarn waves nearest to the end of the packages are more highly stable ones land are complementary to yarn waves spaced inwardly therefrom, and preferably the yarn Wave in at least one of the reversals in the progression is characterized by CII rice

a curvature of the smallest possible radius which it will retain with consistency while in or on the package; however, in some applications axial slippage may be tolerable in the reversals of smaller radius.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a Kwinding apparatus useful in the practice of this invention.

FIGS. 2-7 are developed views of multi-cycle barrel cams.

FIG. 8 is a cross-section of a package wound with a single cycle barrel cam.

FIG. 9 is a fragmentary developed view of two yarn package reversals of different stroke lengths but essentially the same configuration formed in a two-cycle trarverse program.

FIG. l0 represents a cross-section of a package wound with two-cycle traverse program of FIG. 9.

FIGS. ll and l2 are fragmentary developed views of yarn package reversals with different configurations in successive yarn reversals with the use of outback in the yarn profile of the outer reversal indicated in FIG. l2.

DETAILED DESCRIPTION OF THE ILLUSTRATED' EMBODIMENTS The present invention is useful in a windup apparatus of the type shown in FIG. 1, which comprises a frame 13 which carries a cam assembly 10 and a fixed drive roll 5 coupled to a motor 6. A bobbin 7 is situated on a support 8 which is carried on a pivoted arm 9 which is adapted to urge the bobbin 7 or the growing package 2 against the drive roll 5. A typical cam apparatus 10 generally comprises a barrel cam 1 of diameter D on a shaft 11 mounted for rotation in bearings in fixed pedestals 19 to which are secured spaced, parallel guide rails `4 which hold a cam follower-traverse guide 3 in engagement with a cam groove 14 in the barrel cam 1 thus Ibeing Iadapted to traverse yarn 15 as it advances from guide 16 toward the drive roll 5 and thence to the package 2.

The yarn is swept back-and-forth in a zig-zag pattern by means of the barrel cam 1 and deposited on the peripheral surface of the drive roll 5 which carries the yarn to the point of tangency with the bobbin 7 or package 2 where the yarn is deposited or printed on the surface of the package 2. The yarn could, of course, be deposited directly on the package. The barrel cam 1 is a generally cylindrical body having helical grooves of opposite hand in its peripheral surface which intersect and merge in curving reversals to form an endless cam groove. Of interest in the present invention are multi-cycle cams which have a plurality of righthand (RH) and lefthand (LH) grooves which are arranged in alternation sequentially as further described below. Considering the displacement of any biarrel cam or of its follower, measured axially, a single cycle comprises the displacement of the follower through two complete strokes so as to return it to its starting point.

According to the present invention, one cam includes a plurality of cycles of different cam profile as will be described in detail. Typically, the serially connected grooves in the surface of one cam barrel may number from two to about six or more, called dual cycle, triple cycle, quadruple cycle, etc. A dual cycle cam is shown in a developed view, FIG. 2, and comprises two each RH and LH helices in alternation in a length of vrD representing the entire surface of a given cam of diameter D (FIG. 1); therefore the two cycles must be complete in a single revolution. In similar fashion, a triple cycle cam is shown in FIG. 3, the length of which is identical to the cam surface of FIG. 2 or, in other words, the cam barrels have the same diameter D.

lIf additional cycles are crowded into a single cam of a given diameter, a situation will be reached at which the cam may become inoperable because the pressure angle P will become too large; therefore, for dual cycle cams and upward it becomes necessary to arrange the entire cam ygroove program so that it extends over an integral plurality of revolutions of the cam of unlike number or, stated differently, the number of cycles divided by the number of revolutions of the cam to accomplish that number of cycles will be a noninteger but must be a common fraction such as 2/3, 3/5, %/3, etc. Cams arranged accordingly are shown in FIGS. 4-7. The longer portion of each iigure shows the exact plural number of cycles in a given cam (which for any given cam is called a program) While the short section at the left with a length of vrD represents the circumferential surface of the cam. In this latter section all of the grooves of a given cam (i.e., the program) are depicted using dotted lines for that part of the program not contained in the first cam revolution. It may be seen that the use of a plural number of cycles introduces intersections in the grooves known as Crossovers which are negotiated readily by cam followers known to the art. f In the present invention, the individual successive cycles of a given cam having a plurality of cycles have different strokes and different reversal patterns; in addition, cams having three (or more) cycles each of different stroke length may have the various cycles arranged in different sequence from one cam to another. The primary intent in providing these differences is to make the cycles comprising any particular program self-compensating in terms of the patterns of yarn laydown, as will be further described, so as to avoid package defects, e.g., hard shoulders, ridges on and inboard of the shoulders, soft ends or other regions, overthrown chordal sections and the like. The invention contemplates a variety of cycle programs as enumerated in part in Table I in which each capital letter A, B, C, D, etc., represents a different type of cycle, i.e., a different reversal prole, while the separation of letters by a hyphen represents a difference in stroke length of the two cycles on opposite sides of the hypen.

TAB LE I Number of cycles per pm gram Type of program Program Number Vrd I AAAA-B-o In general, raised shoulders or circumferential bands on the periphery of a yarn package result from a surplus of yarn in a given increment of package length as compared with some other increments of like length elsewhere; the existence of the shoulders, at least in part, is due to localized decreases in traverse velocity during which the yarn will tend to pile up, it being understood that the yarn is approaching the package at a constant velocity measured along its length. Such changes in traverse velocity invariably occur in the reversal regions which suggests that the reversals be accomplished in zero package distance which, of course, is not practical because it leads to infinite accelerations which cannot be tolerated by traversing mechanisms. Recognizing that any practical reversal is less than perfect, then, according to the present invention successive reversals are tailored as to velocity profile and thus as to rate of yarn laydown so as to be complementary to each other in terms of quantity of yarn deposited on the package per unit of axial length.

The efficiency of yarn reversals may be defined in terms of the quantity (length) of yarn they contain between the terminii of the truly helical parts of the yarn path,

thus two intersecting helices with zero radius at the reversal have zero yarn in the actual reversal and may be considered to be efficient and any yarn reversal exhibiting a finite radius is therefore less ecient. If a highly efficient reversal is employed on the inner of two or more cycles having unequal stroke length, then it follows that the degree of tailoring required in the longer stroke cycle or cycles will be less than would be the case if a reversal of 10W efliciency had been selected for use on the short stroke cycle. For this reason a reversal of maximum yarn curvature (minimum radius) while not absolutely necessary, is preferred for use on inner reversals of the plural cycle cams of this invention. Any conventional reversal of high efliciency may be used. Considering the inner reversal of a dual cycle type cam as in program number IIa, this reversal, if used in a single cycle cam, will tend to wind a package having a profile in cross-section as shown in FIG. 8 Where a peripheral ridge or shoulder 18 appears; this is greatly exaggerated (10X or more) in its vertical or radial dimension for purpose of illustration. Any ordinary or prior art type reversal will produce such a shoulder but the elfect may be minimized -by use of a maximum curvature (high eiciency) type reversal. If now a second cycle of longer stroke is added, then the magnitude of the shoulder 18 will immediately decrease since half the reversals are now at a different site. If these two yarn reversals of different stroke have like characteristics as shown in the fragmentary developed view. FIG. 9, comprising an inner reversal 19 and an outer reversal 20, then the resulting package profile will appear as in the cross-sectional view, IFIG. 10, and will now have two shoulders 18 and 23 at each end. The inner shoulder 18 will be higher than the outer one due to the fact that the inner shoulder contains the yarn leading into and out of the outer reversals; this latter yarn in the region of the shoulder 18 for this embodiment lies in substantially purely helical paths and thus contributes significantly to the height of the shoulder 18, The existence of outer shoulders of lower radial height than inner shoulders is highly disadvantageous for the reason that a yarn reversal being deposited on such a shoulder tends to lose tension which then leads to other difficulties. Because of this difference in radial shoulder heights, the present invention preferably employs corrective compensation in the yarn profile of the outer or more stable reversal but substantially only in that part of the reversal which lies axially outside the inner reversal. Referring to FIG. l1, in the reversal 24 this compensation is in the direction of increasing the circumferential length of the reversal. Such a reversal 24 is sometimes called a mild or slow reversal and results in a greater rate of yarn laydown in the increment of package length next to the end of the package. This increment is entirely clear of the peak of the inner reversal 19, and has substantially no effect on the latter. It will be realized in effecting this compensation that the magnitude of the circumferential distance over which the slow reversal persists is a function of the amount of yarn it is desired to lay down in the end increment of the package for the purpose of equalizing the height of inner and outer shoulders, if present.

While the foregoing invention represents an improvement in the art, a still further improvement may be effected, in another embodiment, comprising the use of cutback in the yarn prole of the outer reversals. This outback must be situated substantially within the same axial space occupied by the inner reversals. Referring to FIG. 12, the non-helical portion of the inner reversal 19 is situated in the region between the lines 25, 26 (in a package these, of course, are planes). As stated above, since the mere existence of outer reversal yarn in this region contributes to the height of the inner shoulder, then this outer reversal yarn must pass through this region of the inner reversals with dispatch. An upsurge in velocity of traverse, or cutback 27 in the reversal 28 will accomplish this. Since the yarn guide-Cam fQlloWet iS 11C* celerated to a high velocity in the cutback 27 region, compensatory deceleration is resorted to immediately outside (i.e., to the left of) line 2S followed by a slow reversal. Cutback is also preferably employed on the opposite slope of the same outer reversal 28 but need not necessarily be employed contingent on the magnitude of inner shoulder buildup; that is, cutback may be used to merge into either the RH or the LH helical part of the outer reversal 28 or both. It will be realized also that the tangent 29 to the respective cutback curves at their inflection points may have different slopes consistent with acceptable levels of cam pressure angle or of rate of acceleration.

In the dual cycle cam embodiment program IIa, advantageous use was made of a slow outer reversal; it will be realized, however, that under some circumstances such a reversal may be too gradual, that is,.some of the yarn lying in the individual peaks of the reversals may tend toward parallelism with the nominal end of the package and each may have great enough length to constitute a structural fault; a plurality of these present a kind of rippled, shaggy appearance in the end of the package which is undesirable. The cure for this is to increase the relative number of outer reversals (e.g., AA-B type program) versus inner reversals while simultaneously decreasing the slowness of the outer or A reversals. Thus the program of the present embodiment preferably comprises two long-stroke, A type reversals for every one of the relatively shorter stroke B type reversals. The same general plan is adhered to as in the dual cycle program, that is, the A type reversals are slow (but not as slow as in the dual cycle program), while the -B type preferably are of maximum efficiency, i.e., of greater curvature.

What is claimed is:

1. In a process for winding yarn on a bobbin into a cylindrical-bodied yarn package including the steps of rotating the bobbin to wind yarn thereon and traversing the yarn axially through successive stroke lengths to form a package of layers of helical coils, each coil having substantially the same helix angle and being laid down in its reversals in a curve, the improvement comprising laying said coils down in their reversals in differently shaped curves in a repeating progression and at said substantially same helix angle.

2. The process as defined in claim 1, successive reversal curves and corresponding stroke lengths in said progression being different.

3. The process as defined in claim 1, as least two successive reversal curves and corresponding stroke lengths in said progression being the same, the remaining curves and stroke lengths in said progression being different therefrom.

4. A cylindrical-bodied yarn package wound on a bobbin in layers of helical coils having substantially the same helix angle formed by successive strokes, each of said coils having reversals in the form of a curve, there being a repeating progression throughout the package of at least one helical coil having reversals of one shape followed by at least one other helical coil having reversals of another shape. i

5. The yarn package as defined in claim 4, there being a repeating progression throughout the package of two successive helical coils having reversals of one shape followed by one helical coil having a reversal of another shape.

6. The yarn package as dened in claim 4, the strokes corresponding to said one coil and said other coil being of different length.

7. The yarn package as defined in claim 5, the strokes corresponding to said two successive helical coils being the same length, said strokes being different from the corresponding stroke of said one helical coil.

References Cited UNITED STATES PATENTS 1,957,979 5/ 1934 Richter 242-43.1 2,285,438 6/1942 Jones 242-178 2,285,439 6/ 1942 Jones 242-43 2,608,354 8/ 1952 Whittaker 242-43 3,402,898 9/1968 Mattingly 242-43 FOREIGN PATENTS 79,536 9/ 1950 Czechoslovakia 242-43.2 255,930 2/ 1949 Switzerland 242-43 STANLEY N. GILREATH, Primary Examiner U.S. Cl. X.R. 

